The present invention relates to an electrical machine having a rotor which has at least one radial cooling slot and axially running cooling ducts which issue into the at least one radial cooling slot in said rotor. The present invention also relates to a method for cooling an electrical machine having a rotor by cooling the rotor with a cooling stream which is introduced axially into the rotor.
In principle, it is necessary to supply uniformly cool air (or cooling agent) to the rotor of an electrical machine. At the same time, it should be possible to encapsulate the magnet pockets for protecting the magnets against corrosion and movement without a great amount of work.
A type of synchronous machine with permanent magnet excitation and only one core element has been built to date. This has the advantage that the stator in the central region cannot be supplied with a sufficient amount of cooling air. In addition, the rotor is only non-uniformly cooled when the stream of cooling agent floods in. In the case of another type of synchronous machine with permanent magnet excitation, the magnets were fixed (for example by adhesive bonding) on individual core elements. Although more uniform cooling was achieved in this case, it is very complicated to protect the magnets against displacement or against corrosion by encapsulation.